Margin preparation method and machine



Nov. 17, 1970 Q w. SAWERT 3,540,168

MARGIN PREPARATION METHOD AND MACHINE Filed Feb. 26. 1968 INVENTORWALTER SA WERT ATT'Y.

United States Patent York Filed Feb. 26, 1968, Ser. No. 708,334 Int. Cl.1324b 1/00, 31/00; B24c 1/00 US. Cl. 51317 3 Claims ABSTRACT OF THEDISCLOSURE This apparatus is a particle abrasion machine for can bodyblank margin preparation. Can body margins are abraded to fresh baremetal surface in preparation for Welding by passing the can blank edgesbetween elastomeric rolls which rotate as they pass both sides of theblank sheet. At the same time free flowing abrasive grit is fed into thespace between the rotating roll and the sheet material and is thuscarried by the rolls to the sheet margin. The grit acts as many cuttingedges which cut dirt and other matter from the surface on each side ofthe sheet. The grit and waste material fall together from the rolls intoa collector through which a current of air passes. Suitable means returnthe grit to the hopper. The separation of grit from waste material isaccomplished by a magnet, air blast, or other means.

My invention relates to an abrasion method and abrasion machine andparticularly to a machine for abrading body blanks which haveelastomeric rolls to control cutting pressure and an automatic gritreturn system for cooling and repreparation of the grit in its passageback to the hopper.

In the past abrasive wheels have been used to prepare each side of themargin of the body blank and cut the surplusage off to leave bare metal.This device is unsatisfactory due to wear of the abrasive wheels, theneed to carry the heat of friction away by water or other means and thedulling of the abrasive wheels by the material of the body blank.Further, the cutting pressure with which the abrasive wheel bearsagainst the body blank is given by the binding compound of the wheel andcannot be regulated because of the aforementioned conditions and,therefore, the abrasive wheel takes too much or too little off of thebody blank margins, particularly when there are pronouncedirregularities in the margins.

Another means formerly used is a rotating sharp wire brush. However, thewire ends of the brushes lose their sharpness very rapidly and quicklybecome inefficient. The use of sharp wire brushes produces a non-uniformresult and is expensive because the sharp wire brushes wear out rapidlyand must be resharpened frequently.

It is an object of my invention to provide a machine capable ofdependably cleaning the margins of can body stock to the bare metal inan economical manner.

It is another object of my invention to provide a machine for cleaningthe margins of the can body stock with a minimum of heat generation bythe provision of many cutting edges which in their mass provide rapidheat dissipation from the margin.

In brief, my invention is a method and means for abrading the edges of abody blank in preparation for later welding. The edges of a body blankare moved between counter-rotating elastomer rolls so that the rollspress upon opposite sides of the body blank edge with a predeterminedpressure. An abrasive grit is fed from a hopper into the space betweenthe blank and the roll and is carried by the rotating roll against themargin of the body blank. After the abrasive grit has cut the margin ofthe body blank, a current of gas may sweep the grit and the residuesinto a collector and then the grit is conducted back into the hopper.

In order to enable the invention to be more fully understood, referenceis made to the drawings in which the figures show an embodiment of myinvention.

FIG. 1 shows a cross-section view of my apparatus.

FIG. 2 shows a side elevation of my apparatus.

FIG. 3 shows a detailed illustration of the operation of a part of myapparatus.

The machine illustrated and described shows the overall construction ofa margin abrasion machine and each essential element of the machine. Asshown in FIG. 1 an elastomeric surface element 1 is pressed against themargin of a body blank 2 and brushes it with a light pressure. Theelastomeric surface element may be a pair of elasltomeric rolls 1turning in counter-rotation and mounted side by side. A sheet 2 of thematerial to be cleaned or prepared for welding is passed between them.The elastomeric rolls 1 may be of natural rubber, properly selectedsynthetic rubber, polyurethane or other wear resistant material which iselastomeric and can be made harder or softer and should be of astiffness equivalent to soft or medium hard rubber with a durometerreading of less than about 70. These rolls 1 may be made of materialssuch as, polyurethane; fluoro-elastomers; polybutadiene, neoprene andbutyl or natural polyisoprene rubber. In this way a proper loading forcecan be placed upon the roll commensurate with the objectives of avoidingunnecessary heat and thus causing reoxidatiorr of the cleaned metal at ahigh temperature. The particle feed hopper 3 found above the rollsserves as a container for the storage of grit to be used in the abradingprocess. Hopper 3 may be of any size or shape and its dimensions form nocritical part of this invention. In the bottom and sides of the hopperis a slot 4 through which the sheet of body blank material protrudes topass between the elastomeric rolls. The sheet 2 is supported andpositioned by guides 5 above and below it. These guides 5 and 6 may bemade of steel or nylon or may be roller hearings or the like.

The body blank is moved along by means of an endless belt 7 as shown inFIGS. 1 and 2. The belt 7 presses against both sides of the blank 2 inorder to form a firm contact with the blank stock 2. As feed belt 7moves, for example, out of the plane of the paper, FIG. 1, the bodyblank moves with it out of the plane of the paper and passes betweenelastomeric rolls 1. The belt 7 passes forward out around particle feedhopper 3 and goes back along the outside of the hopper to form thereturn part of the endless feed belt. The endless feed belt may beactuated by a variable speed motor (not shown) so that the speed of theblank stock may be adjusted to that speed most suitable to theparticular body blank material, grit and roll pressure employed in theprocess. In order to protect the blank stock and the inner part of theendless belt a shroud 8 (part of the feed hopper) is placed about theseelements. Shroud 8 and the side wall 9 of the hopper 3 form an open slot4 to feed the grit 10 between the elastomeric rolls 1.

Underneath the elastomeric rolls is a collection or gathering device 11for the abrasive grit and residues 12 from the sheet. The abrasive gritand residues 12 fall from the interface between the sheet 2 and theelastomeric roll 1 and into the collecting device 11. The mixed grit andwaste material 12 is conveyed through the collection pipe 14. A suctiondeveloping pump 13 may be used to cause a fluid current to sweep thegrit and grindings down through the funnel and out a collection pipe 14to be deposited finally in the grit feed hopper '3.

While the material is being conveyed the grit and waste may be separatedby air separation, magnetic separation or any other separating processbefore the grit is returned to the particle hopper.

Taking another view of the apparatus, FIG. 2 shows more clearly the feedhopper 3 and its relation to the elastomeric roll 1 and particlecollector 11. The upper guide 5 and lower guide 6 in applicants machineare shown with the blank stock 2 sliding and held in avertical positionbetween them. The feed belt 7 passes for some length in contact with theblank stock so as to insure a good contact and to allow space for one ormore abrasive wheels at various stations to operate upon the margin ofthe blank stock. 9

It is contemplated that the cutting material or grit 10 can bealuminum-oxide; zirconium-oxide; diamond dust; steel grit or any of thecommonly used abrasive materials. In general, the ideal shape of thegrit grain should be tetrahedral for highest efficiency as opposed to.spherical, for example, because the tetrahedral shape gives an abradingor cutting action whereas the spherical shape results in primarily asliding and burnishing action.

The composition and qualities of the elastomeric r01 1 play a criticalpart in this invention. This roll is made of a material having a highWear resistance and the elasticity of the roll may be varied by varyingthe composition to have a firmness between medium or soft stiffness witha durometer reading of less than about 70. An adjustable spring pressesthe elastomeric roll against the blank stock with a predetermined force.The pressure from this elastic spring 15 and the resilience of the roll1 presses against the grit particles in the interface between the movingblank stock and the rotating elastomeric roll (FIG. 3). The surface ofthe elastomeric roll holds the grit during the cutting time and assuresconstant pressure and seating. This pressure is sufficient to cause thegrit to cut all the surface layers from the surface of the blank stockleaving fresh metal exposed after the blank stock has passed through andbeyond the elastomeric roll or rolls. 1

Constant operating conditions are assured because the elastomeric roll,for example, polyurethane, or any other wear resistant elastomericmaterial such as those set forth above does not wear appreciably andfresh grit is continuously fed into the interface between the blankstock and the elastomeric roll. Any desired pressure is brought to bearbetween the blank and the roll by adjusting, the spring pressure and byusing a roll of stiffness suitable to the material being abraded and thegrit em-' ployed. The cutting quality of the grit is assured bycontinual purification of the grit and continual change of the exposededge of the grit particle as the grit passes the blank stock in eachcycle. Most of the heat generated in the process is carried away by thegrit. These operating conditions are set to produce a clean freshsurface at the margins of the body blank for welding and this surfacewill be as cool as possible because of the coolness and sharpness of thegrit, the pressure of the controlled elastomeric roll and the coolingeffect of the air current on the moving parts of the machine.

If the material to be cut from the surface of the body blank isdifficult to abrade in a single step or if heat generated in the bodyblank by the cutting step causes quick reoxidation of the surface of thebody blank then a second abrasion machine using suitable material toreclean the margin may be located (or a second abrading station) furtheralong the body blank feed line so as to provide a clean, fresh, cooluniform blank margin as an end product, i

An advantage of my machine over the prior art is that due to controlledcutting pressure the blank stock will leave the machine in a coolcondition so that the fresh surface which may be exposed to air is notquickly reoxidized and the stock may be held for an interval beforebeing welded.

Another advantage is that the fresh surface of the prepared blank stockis comparatively uniform from blank to blank in a long run since theabrasive conditions will change relatively little. r 7

Another advantage is that it is not necessary to change machine parts orsettings frequently since the elastomeric roll and 'grit lasts arelatively long timewithout appreciable change of quality.

The final advantage is that the cutting pressure remains relativelyconstant and cutting edges remain sharp in this machine thereby assuringuniformly cleaned margin surfaces.

The foregoing is a description of an illustrative embodiment of theinvention, and it is applicants intention in the appended claims tocover all forms which fall within the scope of the invention.

I claim 1. A method of preparing the margins of a body blank for weldingcomprising the steps of:

pressing elastomeric surface means against the margin of a body blank,

feeding grit to the interface between said body and said elastomericsurface,

moving said elastomeric body means relative to said body blank, wherebysaid grit abrades said body blank to produce residues, and

passing a cool current of gas adjacent to said elastomeric surface toconduct said grit and residues away from said interface and for thepurpose of cooling said elastomeric surface, body blank and grit.

2. The method of preparing the margins of a body blank for Welding asset forth in claim 1 having the additional step of:

conducting the grit and residues'fallin-g from said interface to apurifying means, and I conducting the purified grit back to saidinterfaces whereby said grit at said interface presents a different edgeto said body blank at each cycle to give a maximum cutting efficiency.

3. The method of preparing the margins of a body blank for welding asset forth in claim 2 and the additional step of: I

repeating the steps of claim 2. to cut away any foreign material left onthe body blank as it passes a second abrading station.

- 1911 Great Britain. 1 3 1926 Great Britain. 9/ 19 13 France. 10/ 1911Germany.

JAMES L. JONES, 111., Primary Examiner

